MATLAB Answers

Draw growing circles on a jpeg file.

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Ranjan Sonalkar
Ranjan Sonalkar on 20 Oct 2017
Commented: Ranjan Sonalkar on 20 Oct 2017
I have read in a jpeg file of a floor map. Now I want to draw a circle on it of time-dependent radius, so that it appears to be growing with time. I used the function viscircles. At a later time I want to go to a different position within the image and start drawing a new circle. But viscircles draws a filled circle that is persistent. How can I plot new circles and make the earlier circle go away. I could use cla every time I want a new circle, but that would require me to display the background image again. That would add processing time.

Accepted Answer

Jan
Jan on 20 Oct 2017
Edited: Jan on 20 Oct 2017
You can remove the object by the delete command:
image(rand(640, 480, 3) * 0.5);
h = viscircles([200, 200], 5);
pause(1)
delete(h);
  1 Comment
Ranjan Sonalkar
Ranjan Sonalkar on 20 Oct 2017
Thanks, works as I would like it to.

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More Answers (1)

Geoff Hayes
Geoff Hayes on 20 Oct 2017
Ranjan - according to viscircles, if you do something similar to
hg = viscircles(ax,centers,radii)
then h is a handle to an hggroup object. As such, you should be able to hide these circles (if you wish by setting the Visible property to off, see hggroup properties) or you should be able to just delete this object
delete(hg)
The following example illustrates this
hg = hggroup;
x = -2*pi:0.4:2*pi;
y = sin(x);
line(x,y,'Parent',hg)
The sine curve is drawn and then we can delete is with
delete(hg)
  1 Comment
Ranjan Sonalkar
Ranjan Sonalkar on 20 Oct 2017
Thanks, works as I would like it to.

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